Treatments for virus-induced diseases of the central nervous system (CNS) are sub-optimal or non- existent. Virus infection of the CNS results in a robust host neuroinflammatory response, defined by the activation of resident CNS immune cells (microglia and astrocytes) and the up-regulation of pro-inflammatory genes. The role of these responses in virus-induced CNS disease remains unclear. Neuroinflammatory responses likely play a protective role in facilitating the removal of infected cells and the recovery of damaged neurons. However, many of the factors released by immune cells may contribute to injury within the CNS. Indeed, neuroinflammation is a key pathogenic component following neurologic injury and during non- infectious forms of neurologic and neurodegenerative disease. West Nile virus (WNV) is the most common cause of epidemic encephalitis within the US. This proposal will investigate neuroinflammatory responses induced by WNV-infection and will evaluate neuroinflammatory processes as potential therapeutic targets for WNV-induced CNS disease. Since neuroinflammatory responses are central to a variety of CNS injury and disease pathologies, including neurodegenerative diseases, the proposed experiments will likely have wide reaching clinical implications. Microglia and astrocytes are the first cells to respond to disturbances within the CNS and likely play a key role in neuroinflammation both as effector immune cells and by influencing subsequent responses generated by immune cells that infiltrate the CNS from the periphery. Activation of microglia and astrocytes can also lead to specific mechanisms of neuronal death by reactive oxygen species (ROS), such as nitric oxide (NO), and glutamate excitotoxicity. The role of resident CNS cells in virus-induced neuroinflammatory responses is unclear since infiltrating immune cells produce many of the same pro-inflammatory molecules. The proposed studies will use ex vivo slice cultures, sub-regions of these cultures, and isolated CNS cell populations, to determine the contribution of CNS resident cells (microglia and astrocytes) to neuroinflammatory responses, and cell death pathways associated with these responses, that are generated in the CNS following virus infection. In these studies the expression of pro-inflammatory and cell death associated genes following virus infection will be determined at the mRNA and protein level by quantitative polymerase chain reaction (qPCR), enzyme-linked immunoabsorbent assay (ELISA), western blotting and/or fluorescence-activated cell sorting (FACS). The proposed studies will also evaluate microglia and astrocytes as therapeutic targets for virus-induced CNS disease. Microglial and astrocyte activation/activity will be inhibited in ex vivo and in vivo models of viral pathogenesis using a combination of genetically modified animals and pharmaceutical treatments. The effect of microglia and astrocyte activation on viral-pathogenesis will then be evaluated using well established markers of virus-induced CNS disease, including viral titer, virus-induced injury and apoptosis and survival studies.